O'Fallon Tap Water Quality Report
O'Fallon's water has 3 contaminants above EPA MCLGs. Consider using a certified water filter for additional protection.
No single water system serves most of O'Fallon (95,355 residents, Census 2024 estimate). Its large systems are OFALLON PWS (EPA counts 32,515 people served, about 34% of O'Fallon's population); ST CHARLES COUNTY PWSD 2 (EPA counts 100,587 people served, more than O'Fallon's population). EPA's counts may include people served outside O'Fallon, so each share is at most that. Check which one bills you: each system's figures are shown separately below.
- OFALLON PWS: 199 contaminants tested, 3 above EPA MCLGs; health-based violations since 2020: 0
- ST CHARLES COUNTY PWSD 2: 206 contaminants tested, 4 above EPA MCLGs; health-based violations since 2020: 0
Other systems listed for O'Fallon with results above guidelines: ST CHARLES COUNTY PWSD 2 (4 above guidelines)
Water systems
2 large systems
Residents (Census 2024)
95,355
Health-based violations since 2020
0
OFALLON PWS. EPA SDWA violation data as of Q2 2026 (downloaded 2026-07-09).
Latest sample on file
Aug 2025 · OFALLON PWS
Utilities publish newer results in their annual water quality report (Consumer Confidence Report).
Is O'Fallon Tap Water Safe to Drink?
We recommend using a certified water filter for additional protection, especially for vulnerable populations like children, pregnant women, and those with compromised immune systems. O'Fallon's water has 3 contaminants above EPA health-based guidelines (MCLGs), while it meets federal legal limits.
OFALLON PWS, O'Fallon's water system, serves 32,515 people. 1 other system is listed for O'Fallon. Each system's results are listed under its own name, never added to OFALLON PWS's. Water quality testing is conducted regularly and reported to the EPA. The latest sample on file for OFALLON PWS is from Aug 2025.
In EPA's 2023–2026 UCMR 5 testing, OFALLON PWS measured lithium at up to 71.3 µg/L, which EPA counts as above its health reference level of 10 µg/L. That level is a screening value EPA uses to decide what to study further, not a legal limit, and this result does not change this page's water-quality summary.
Boil water advisories are issued by water systems and state agencies, and they change from day to day. Boil water advisories in Missouri
O'Fallon Water Service Areas
What these numbers actually mean for O'Fallon, MO
We read O'Fallon, MO’s published record and send you a short report — which findings warrant a decision, which to ignore, and what to do about it. Including when the answer is nothing.
- 3 contaminants above EPA MCLGs and 10 contaminants with an EPA health goal detected in some samples (no level on file)
- 196 results on file
- 23 PFAS compounds on record
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Recommended Water Filters for O'Fallon
Based on O'Fallon's water quality data, these NSF-certified filters are recommended to remove contaminants above EPA MCLGs.
Solventum Purification Inc.
3MRO401
NSF Certified:
Daily Production
11.48 gpd
Highlights:
- NSF-58 certified reverse osmosis system
- 11.48 GPD production capacity
- Reduces total dissolved solids (TDS) for purer water
Removes 15 contaminants:
+10 more
Copper, Cryptosporidium, Fluoride, Lead, Radium 226, Radium 228, Radium, combined (-226 & -228), Selenium, Total Dissolved Solids, Turbidity
Solventum Purification Inc.
3MRO301
NSF Certified:
Daily Production
11.48 gpd
Highlights:
- NSF-58 certified reverse osmosis system
- 11.48 GPD production capacity
- Reduces total dissolved solids (TDS) for purer water
Removes 15 contaminants:
+10 more
Copper, Cryptosporidium, Fluoride, Lead, Radium 226, Radium 228, Radium, combined (-226 & -228), Selenium, Total Dissolved Solids, Turbidity
Culligan
ZeroWater
NSF Certified:
Flow Rate
1.9 gpm
Daily Production
1 gpd
Highlights:
- Compact design
- Easy to set up
- Affordable
- NSF-42, NSF-53, NSF-401 certified
Removes 19 contaminants:
+14 more
Strontium, Molybdenum, Fluoride, Uranium, Lead, Total PFAS, Chlorine, 25, Phosphorus, Bicarbonate, Calcium, Carbonate, Magnesium, Sodium
Santevia
Bath Filter
NSF Certified:
Flow Rate
0.36 gpm
Highlights:
- Organic cotton design reduces plastic used in construction
- Affordable upfront & ongoing cost
- The only bath filter that removed 100% chlorine with “normal” faster faucet flow
Removes 1 contaminants:
Verify Your Water Quality with Independent Testing
With 3 contaminants above EPA MCLGs and 10 contaminants with an EPA health goal detected in some samples (no level on file), independent laboratory testing provides a second opinion and can track changes over time.
SimpleLab
Advanced Home Water Test
$269
Comprehensive water analysis testing over 200 contaminants including bacteria, heavy metals, and chemical compounds.
Tap Score
Advanced Microplastics Test
$829
Cutting-edge testing for microplastics particles in drinking water using advanced laboratory techniques.
Tap Score
Haloacetic Acids (HAA9) Test
$275
Tests for disinfection byproducts formed when chlorine reacts with organic matter in water treatment.
With 3 contaminants above health guidelines, you may want to explore water purification options. Learn how to make distilled water at home for applications like humidifiers, CPAP machines, and baby formula.
What O'Fallon's water readings can explain
Utility-reported data for O'Fallon includes iron, manganese, sulfate and a chlorine-based disinfectant — the readings behind these common tap water questions. We publish a city-level hardness figure for O'Fallon, resolved from its water systems where they report one and estimated from county sampling where they do not. Each page starts with the hot-tap and cold-tap check, then shows what your own water system reported.
On a private well near O'Fallon? Public-water results do not apply to private wells. See St. Charles County well water testing and USGS risk data — modeled arsenic, nitrate, and the tests to run.
Water softener cost and installation in O'Fallon
O'Fallon's tap water measures 6.5 grains per gallon (112.0 mg/L) — moderately hard on the USGS scale, below the range where scale is usually worth treating.
Water softener cost for 6.5 gpg water in O'Fallon — equipment and local installation labour for your ZIP code, with the sizing arithmetic shown in full. For the national picture first, read what a water softener costs — equipment, installation labour and ten-year ownership, each separated out. For Missouri as a whole, read water softener cost in Missouri — priced against the plumber wage published for the state.
Frequently Asked Questions About O'Fallon Tap Water
O'Fallon's water has 3 contaminants above EPA MCLGs. While the water meets federal legal limits, we recommend using a certified water filter for additional protection, especially for vulnerable populations like children, pregnant women, and those with compromised immune systems.
Spotted something off on this page?
Residents keep our data honest.
This form corrects our data; it does not reach OFALLON PWS. For a problem with your water now (discolored water, no water, low pressure, a leak), contact OFALLON PWS directly.
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